﻿using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

namespace MP3Ganizer.Services.Tagging
{
    public class LevenshteinServices
    {
        Dictionary<CoupleOfString, double> _percentagesMatching;

        public LevenshteinServices()
        {
            _percentagesMatching = new Dictionary<CoupleOfString, double>();
        }

        public double GetPercentageOfString(string first, string second)
        {
            CoupleOfString current = new CoupleOfString(first, second);
            if (_percentagesMatching.ContainsKey(current))
            {
                var keyValuePair = _percentagesMatching.FirstOrDefault(item => item.Key.Equals(current));
                return keyValuePair.Value;
            }
            else
            {
                var percentage = GetPercentageOfString(first, second);
                _percentagesMatching.Add(current, percentage);
                return percentage;
            }
        }

        /// <summary>
        /// Compute the distance between two strings.
        /// </summary>
        private int Compute(string s, string t)
        {
            int n = s.Length;
            int m = t.Length;
            int[,] d = new int[n + 1, m + 1];

            // Step 1
            if (n == 0)
            {
                return m;
            }

            if (m == 0)
            {
                return n;
            }

            // Step 2
            for (int i = 0; i <= n; d[i, 0] = i++)
            {
            }

            for (int j = 0; j <= m; d[0, j] = j++)
            {
            }

            // Step 3
            for (int i = 1; i <= n; i++)
            {
                //Step 4
                for (int j = 1; j <= m; j++)
                {
                    // Step 5
                    int cost = (t[j - 1] == s[i - 1]) ? 0 : 1;

                    // Step 6
                    d[i, j] = Math.Min(
                        Math.Min(d[i - 1, j] + 1, d[i, j - 1] + 1),
                        d[i - 1, j - 1] + cost);
                }
            }
            // Step 7
            return d[n, m];
        }

        private double CalculatePercentageMatching(String s1, String s2)
        {
            if ((s1 == null) || (s2 == null)) return 0;

            double dis = Compute(s1, s2);
            double maxLen = s1.Length;
            if (maxLen < s2.Length)
                maxLen = s2.Length;
            if (maxLen == 0)
                return 100;
            else return (1 - dis / maxLen) * 100;
        }

    }
}
